In order to guarantee the good operation of a base station communication system, it is necessary to know the standing-wave ratio of the base station system in real time, so the standing-wave ratio of the base station system needs to be detected frequently. In a base station system, vector measurement methods based on Frequency Domain Reflectometry (FDR) technology is widely used to detect the standing-wave ratio.
Frequency domain reflectometry technology is one kind of vector-based measurement technology, whose basic principle is: a set of swept-frequency sine signals is injected into a cable under test, and then reflected signals generated at breakpoints and other reflection points in the cable under test add or minus the input swept-frequency sine signals to generate a corresponding spectrogram, as illustrated in FIG. 1. The vector sum of the signals generates a waveform along the frequency axis, and Fast Fourier Transform (FFT) is performed to transform the vector sum of the signals into frequency-domain information. Distances of the breakpoints or fault points could be calculated according to relative propagation velocity of the cable. The number of waveforms in the frequency relationship diagram is proportionate to the electrical distances of the reflection points in the cable, and result of the Fast Fourier Transform calculation is a characteristic graph of trouble pots represented by actual standing-wave ratio with respect to distance.
Although the frequency domain reflectometry technology is a vector-based measurement technology and its measurement accuracy is pretty high, algorithm implementation of the technology is quite complicated. In addition, as the frequency domain reflectometry technology requires a swept-frequency signal to be formed as the data source, when applied in a TD-LTE base station system, the frequency domain reflectometry technology needs to transmit a specific training sequence to meet the requirements. However, the special training sequence is an interference source for wireless communication systems, therefore, in the prior art, standing-wave ratio detection can't be frequently performed in a base station system. However, due to the need for good operation of a base station communication system, it is very important to know the change of standing-wave ratio of the base station system frequently or in real time.
In summary, to guarantee the good operation of a TD-LTE base station system, the base station system needs to detect its standing-wave ratio frequently and in real time, while the specific training sequence used in the current frequency domain reflectometry technology will produce additional interferences with the communication system, and will affect the transmission quality of the TD-LTE communication system.